Bezier.java

package curves;

import java.util.ArrayList;

/**
 * Calculate the Bezier curve for a 2-dimensional object using the solution to the matrix equation.
 * @author asevans
 *
 */
public class Bezier {

	private int order=4;
	private ArrayList<PointObject> controlObjects;

	/**
	 * Empty Constructor
	 */
	public Bezier() {

	}

	/**
	 * Set the order (nth power +1)
	 * @return
	 */
	public int getOrder() {
		return order;
	}



	public void setOrder(int order) {
		this.order = order;
	}



	public ArrayList<PointObject> getControlObjects() {
		return controlObjects;
	}



	public void setControlObjects(ArrayList<PointObject> controlObjects) {
		this.controlObjects = controlObjects;
	}



	/**
	 * Get a spline point from four provided PointObject objects
	 * @param p1
	 * @param p2
	 * @param p3
	 * @param p4
	 * @return
	 */
	private PointObject calcPoint(PointObject p1, PointObject p2, PointObject p3, PointObject p4){

		//calc a point on the bezier curve
		PointObject retobject=new PointObject();
		
		//mutliply our matrix by the points which are not in vector form here (no direction needed then)
		float basisax=(float) p1.getX();
		float basisay=(float) p1.getY();
		
		float basisbx=(float)((-3*p1.getX())+(3*p2.getX()));
		float basisby=(float)((-3*p1.getY())+(3*p2.getY()));
		
		float basiscx=(float)((3*p1.getX())+(-6*p2.getX())+(3*p3.getX()));
		float basiscy=(float)((3*p1.getY())+(-6*p2.getY())+(3*p3.getY()));
		
		float basisdx=(float)((-1*p1.getX())+(3*p2.getX())-(3*p3.getX())+p4.getX());
		float basisdy=(float)((-1*p1.getY())+(3*p2.getY())-(3*p3.getY())+p4.getY());
		
		float t;
		
		//get the solution to our new matrix
		for(int i=0;i<order;i++){
			t=i/order;
			retobject.setX(basisax+t*(basisbx+t*(basiscx+(t*basisdx))));
			retobject.setY(basisay+t*(basisby+t*(basiscy+(t*basisdy))));
		}
		
		//return the calculated point object
		return retobject;
	}
	
	
	/**
	 * Control the calculation of the spline points
	 * @return
	 */
	private ArrayList<PointObject> calcCurve(){
		ArrayList<PointObject> po=new ArrayList<PointObject>();
		
		if(controlObjects.size()>0){
			//calc bezier curve
			int i=0;
			
			//add the initial points
			while(i<3 & i<controlObjects.size()){
				po.add(controlObjects.get(i));
				i++;
			}
			
			//add the remaining calculated points
			if(controlObjects.size()>3){
				for(i=3;i<controlObjects.size();i++){
					po.add(calcPoint(controlObjects.get(i),controlObjects.get((i+1)),controlObjects.get((i+2)),controlObjects.get((i+3))));
				}
			}
		}
		else{
			try{
				throw new NullPointerException("No Points Provided!");
			}catch(NullPointerException e){
				e.printStackTrace();
			}
		}
		
		return po;
	}
	
	/**
	 * Run the program and get an ArrayList<PointObject> of spline points.
	 * The number of points returned depends on the number of control points provided.
	 * @return
	 */
	public ArrayList<PointObject> getCurvePoints(){
		return calcCurve();
	}

}